Embodiments of the present invention are related to man-machine systems capable of completing complex mechanical control tasks, and more particularly to blending human operator inputs with inputs derived from sensor measurements for the specified task to improve task performance and reduce operator workload.
By using accurate and appropriate sensors, autonomous control systems can be constructed that can out-perform a human operator for a specific, narrowly defined task. Complex mechanical control missions, consisting of broadly defined tasks executed in any specified order, require a complex autonomous system capable of operating in multiple modes with associated mode switching criteria. Such systems may be susceptible to failure when presented with unforeseen circumstances. A well trained human operator, on the other hand, can adapt to unexpected circumstances and apply judgment in order to complete a complex mission.
Traditionally, the problem of integrating a control system using sensor-derived control inputs with the presence of an expert operator has taken three basic approaches:
1. The operator can act as a supervisor of a full-authority autonomous control system configured to operate in a number of modes, each capable of completing a specific task. The operator is responsible for engaging and disengaging the autonomous system via toggle switches, as well as selecting a mode via momentary switches as appropriate for the specified task. Operator override requires explicit disengagement of the autonomous system.
2. An autonomous control system having a number of modes can provide an operator with “suggested” options via a control panel. In this case, the autonomous system has zero authority and the operator is solely responsible for operating the control inputs.
3. A system having an “outer-loop” control law, using sensor inputs appropriate for a specified task, can generate an automatic input that is added directly to the human operator's input. An authority limit is used to ensure that the operator can override the automatic input.
The disadvantages of the prior approaches to man-machine systems include the following. A full-authority autonomous control system requires that the human operator have expert knowledge of all the modes of operation of the system in order to perform the necessary switching, engage/disengage, and override functions. The operator will be somewhat disconnected from the task, since the autonomous system has full authority, and will be instead relegated to monitoring the system closely to ensure the proper mode is engaged and performed. Any loss of situational awareness regarding engagement or mode state can have catastrophic consequences depending on the criticality of the task. On the other hand, when suggested options are provided by a zero-authority autonomous system, the operator must make an intervening judgment and apply the correct decision. Human operators are subject to considerable neuromuscular reaction delay in response to a flash input, typically in the range of 200 ms, which can severely limit the operator's achievable task performance. In the case of “outer-loop” control law systems, the autonomous control inputs are applied in parallel with the operator's inputs, and although the operator may have the ability to override, problems can arise due to a duplication of control effort when both the operator and the control law are tracking the same objective. Such a duplication of control effort could result in overcompensation by the combined man-machine system. In this case, the operator's must compensate for the effects of the control law as well as the characteristics (dynamics) of the system.